1. Field of the Invention
This invention relates to an apparatus used in a centrifugal separating step for sample preparation in the field of clinical chemistry. Especially, the invention relates to a separating apparatus used for isolating a serum fraction from a freshly isolated blood sample without contamination with a clot fraction.
2. Description of the Prior Art
It has been known that diagnostic tests, especially the diagnostic tests for blood samples are essential in the field of clinical diagnosis, because blood contains essential components for maintaining biological conditions of the body. Such components are blood cells, enzymes, hormones, proteins, sugars and the like, and they mirror the disturbances of the normal working of the body.
In recent years, various kinds of diagnostic tests of blood samples have been developed and used in the field of clinical chemistry. With the advance in diagnostic tests, hospital biochemists and their coworkers have been faced with increasing demands for specialized tasks for testing blood samples. In addition, they also have been faced with increasing demands for routine tasks such as sample preparations for the specialized tests. To meet the demands of these tests, equipment for automatically testing the samples have been developed and provided to hospitals and laboratories. While these analyzers have increased the efficiency of performing the necessary tests, a problem has remained in finding ways and means of isolating a serum fraction without contamination with a clot fraction for supplying the isolated serum for clinical analyses.
Although most of the diagnostic blood tests include a step of separating blood into serum and clot fractions by means of centrifugal separation, it is difficult to prepare a serum fraction quickly and effectively from the blood sample because at least a part of a pellet containing blood cells come off the wall of the tube and spreads out freely in the serum. Therefore, it has been required to carefully handle the centrifuged sample in the tube.
To solve this problem, various types of serum separating methods have been suggested.
One type of the such methods comprises a step of using a device incorporating a chemical substance called a sealant. This sealant is characterized by thixotropic, water insoluble, and substantially non-toxic properties. For example, Michel J. Lukacs and et al., U.S. Pat. No. 3,780,935 issued Dec. 25, 1973, discloses a sealant having a proper specific gravity to divide serum and clot fractions. This sealant comprises essentially of a silicone fluid and an inert filler such as silica dispersed therein. The blood separation using this sealant is accomplished by inserting a device containing a supply of the sealant into a container such as a glass tube holding a sample of blood. In addition, the above device is characterized by a nozzle portion which extends into the sample. During the centrifugation, the device discharges the sealant into the blood. After the centrifugation, the sealant is migrated to a boundary of the two fractions.
Another type of the serum separating methods comprises a step of using a porous plug. For example, Japanese patent application (TOKKYO KOHO number HEI-1-28346) discloses the insertion plug in the shape of a column or a conical frustum, which is made of a multi-porous material and the bottom of the plug is covered with a rigid plate. After the centrifugation, the insertion plug is migrated to a boundary of the two fractions to separate them each other.
However, these conventional devices have some difficulties in fractionation of the blood sample. That is, in the case of the blood fractionation procedure using a high molecular substance such as silicone as a sealant, it is difficult to separate this sealant with the blood fraction. In addition, the physiological or chemical nature of the blood will be changed by adding the sealant. In the case of using the device comprising a multi-porous material, the pores are often plugged with the clot and incomplete fractionation of the blood results.
Furthermore, other types of blood separating means have been proposed. For example, Japanese patent application No SHO-55-130519 discloses a separating device in the form of a frustoconical cylinder having a narrow opening at the top portions thereof to pass serum through the device and projected portions on the side wall thereof to contact with the inner surface of the tube. This device is inserted into the tube after the clot is formed by the agglutination in the tube. However, the time is wasted in waiting to complete the clot-forming process.
Still furthermore, another Japanese patent application (TOKKYO KOHO SHO-56-118669) discloses a separating apparatuses comprising a frustoconical plug and a ring. This ring is slipped on the frustoconical plug by the centrifugal force to separate the serum and clot fractions. However, if the plug is misaligned, the plug does not fit into the ring.
It is noted that the above documents do not disclose how to fit the device to different types of tubes, glass tubes and plastic tubes, which are widely used for general blood separating procedures.
In general, two types of tubes are used for general blood separating procedures. That is, one type of the tube is made of a glass and the other type of the tube is made of a plastic material. The glass tube has a constant or a slightly varying inner diameter, while the plastic tube has a gradient of inner diameter. For example, inner diameters of each portion of a plastic tube (10 ml vol.) are varied from 14.0 mm to 13.0 mm.
Accordingly, it is evident that two types of the serum separating apparatuses must be provided to fit to the different types of the tubes. It is required that when the serum separating apparatus is moved smoothly along an inner surface of the plastic tube during the centrifugation, the device diameter must be changed to fit to the variation of the inner diameters of the tube.
However, the above references do not show any means to solve this problem.